1. Field of the Invention
The present invention relates generally to a human spinal implant device for implantation into intervertebral space between adjacent vertebral bones and to a surgical method for installing such a spinal implant assembly.
2. Description of the Prior Art
Genetic or developmental irregularities, trauma, chronic stress, tumors, and degenerative wear are typical causes which can result in spinal pathologies for which surgical intervention is necessary. Various devices and techniques are disclosed in the prior art for immobilizing and/or fusing adjacent bones by implanting artificial devices in or on the spinal column. The region of the back which needs to be immobilized, as well as the individual variations in anatomy, determine the appropriate surgical protocol and implantation device which is best suited for the case at hand. Where a failure of the intervertebral disc is concerned, the inter-body fusion implant is often chosen.
An inter-body fusion maintains disc height, helps to protect the nerve root and restores weight-bearing ability to anterior structures. The fusion also restores the annular region of the spine to tension and immobilizes the unstable, degenerated intervertebral disc. Anterior approaches and fusion in the cervical region have gained wide acceptance by both neurosurgeons and orthopedic surgeons as treatment for herniated discs, trauma and related degenerative conditions. In the case of lower lumbar spine problems, such techniques have had more sporadic success. Recently, pedicel screws and rods have allowed surgeons to reduce degenerative conditions and immobilize the motion segment, but have not eliminated the need for weight-bearing support for the anterior spinal column.
The prior art implant techniques have generally involved two component implant assemblies. The surgical procedures for installing such devices can be complicated and traumatic to the patient. Although X-ray imaging can be used to determine the approximate location of the respective two component assemblies, alignment of the prostheses can obviously be of major concern.
Accordingly, it is an object of the present invention to provide a new and improved single component inter-body fusion cage which overcomes known deficiencies of the prior art while providing improved overall results.
The apparatus of the invention is an intervertebral prosthesis for implantation between adjacent vertebrae of the human spinal column. The prosthesis comprises a unitary body configured and sized to be inserted between adjacent vertebrae in a single step implantation procedure. The body is banana-shaped as viewed from above and has an exterior surface and an interior surface, the interior surface defining an internal recess for receiving cancellous bone material during an implantation procedure. Preferably, the unitary body is a cage which is formed as interlinked mesh. Most preferably, the banana-shaped cage body is a ring of metal having evenly spaced openings about a circumference of the body. The preferred cage body is formed of a hard metal alloy, such as a titanium alloy. The intervertebral prosthesis is selectively sized to fit within a vertebral disk space of a human anatomy allowing adequate space for additional cancellous bone anterior to the cage body within the disk space.
The method of the invention facilitates inter-body fusion in the vertebral column by providing an improved prosthesis and method of installation. A space is first prepared for receiving a prosthetic device between two vertebrae. The banana-shaped spinal cage body is then surgically inserted into the space between the vertebrae. The banana-shaped cage body has an exterior surface and an interior surface, the interior surface defining an internal recess for receiving cancellous bone material during an implantation procedure. Preferably, the cage body is a ring of metal having evenly spaced openings about a circumference of the body. The cage body forms an interlinked mesh. The preferred cage body is formed of a hard metal alloy. Preferably, the cage body is formed of a titanium alloy.
Additional objects, features and advantages will be apparent in the written description which follows.